I have read a brief of content but it seem like you 're not going to write about How to control bluetooth module.
In my opinion I think that if you could write about using Node.js and some library like noble, bleno to read and write data, then use johnyfive to do things with data, this book could become more attractive because the IOT is the future and bluetooth is IOT 's core.
How about creating bluetooth communication between pi and tessel, pi read temperature sensor value and send that data to tessel? It's not a bad idea right?

Hello! I agree that Bluetooth, especially Bluetooth LE (BLE), is very topical in terms of IoT. Here are some thoughts:

* Chapter 12 in the book covers BLE, with a focus on Web Bluetooth, and experiments with Espruino's Puck.js platform
* The concepts covered in the book could certainly be used on boards that are Bluetooth-enabled. The concepts are, generally-speaking, transport/comms-agnostic.

That being said, I don't want to give the sense that the book dives into any level of detail about Bluetooth or BLE on a protocol level. Bluetooth as a technology in itself is orthogonal to the main thrust of the book, which is about learning hardware essentials through the lens of JavaScript.